Muonium atoms observed in liquid hydrocarbons

Muonium atoms have been observed in n-hexane, c-hexane, and tetramethylsilane at 295 or 273 K by the MSR technique. The yield of muonium in these non-polar liquids is found to be quite comparable to that observed previously in water, methanol, and ethanol. This suggests that neither the dielectric constant of the medium nor the free-electron mobility has a major influence on the formation process. This in turn supports the view that muonium formation does not mainly result from intraspur reactions in the terminal spur of the muon's track.The chemical lifetime of muonium in these hydrocarbons is curtailed by spurious impurities so that high purity is required. In addition, however, there may be a chemical reaction between muonium and the hydrocarbon itself because the maximum lifetime found increases in the order of increasing bond energy. Reaction rate constants with added solutes have also been measured, and these observations open up the possibility of studying hydrophobic solutes and extending hydrogen-isotope studies to biologically-important media.